Samba4 alpha4 is not a final Samba release. That is more a reference
to Samba4's lack of the features we expect you will need than a
statement of code quality, but clearly it hasn't seen a broad
deployment yet. If you were to upgrade Samba3 (or indeed Windows) to
Samba4, you would find many things work, but that other key features
you may have relied on simply are not there yet.
For example, while Samba 3.0 is an excellent member of a Active
Directory domain, Samba4 is happier as a domain controller, and it is
in this role where it has seen deployment into production.
Samba4 is subjected to an awesome battery of tests on an
automated basis, we have found Samba4 to be very stable in it's
behaviour. We have to recommend against upgrading production servers
from Samba 3 to Samba 4 at this stage, because there may be the features on
which you may rely that are not present, or the mapping of
your configuration and user database may not be complete.
If you are upgrading, or looking to develop, test or deploy Samba4, you should
backup all configuration and data.
We welcome your testing, please file bug reports at
https://bugzilla.samba.org/, product: Samba4. Please include as much
information as possible, such as GIT revision number and backtraces.